Thermally conductive nanocomposition and method of making the same

ABSTRACT

A nanocomposite fluid includes a fluid medium; and a nanoparticle composition comprising nanoparticles which are electrically insulating and thermally conductive. A method of making the nanocomposite fluid includes forming boron nitride nanoparticles; dispersing the boron nitride nanoparticles in a solvent; combining the boron nitride nanoparticles and a fluid medium; and removing the solvent.

BACKGROUND

Hydrocarbon and silicone fluids, e.g., oils, can provide electricalisolation between a stator and rotor and also power leads in an electricmotor. Additionally, oils provide lubrication for engines and motors toextend lifetime and prevent failure. Motor oils lubricate surfaces inrelative motion and close contact to one another, such as for example,bearings and other metal surfaces, to improve motor efficiency and motorrun life. Additionally, oils can be useful for carrying away heat thatis generated within the motor, thereby reducing the operatingtemperature.

A broad range of electrical resistivities, thermal conductivities, andfluid properties exist among oils. Oils are generally selected basedupon a desired viscosity at a specified operating temperature.Preferably, oils are selected to ensure efficient operation of a motoror engine at desired operating temperatures by providing sufficientviscosity for lubrication.

Even for electrical devices without moving parts, heat transfer fromstatic components and their electrical isolation are considerations,particularly in high voltage or high current applications. Additionalequipment is sometimes needed to aid the cooling of these devices. Newmaterials for electrical insulation and thermal conduction havingsuitable viscosities would be well-received in the art.

BRIEF DESCRIPTION

The above and other deficiencies of the prior art are overcome by, in anembodiment, a nanocomposite fluid comprising: a fluid medium; and ananoparticle composition comprising nanoparticles which are electricallyinsulating and thermally conductive.

In an embodiment, a method of making a nanocomposite fluid comprisesforming boron nitride nanoparticles; suspending the boron nitridenanoparticles in a solvent, surfactant, or a combination comprising atleast one of the foregoing; and combining the boron nitridenanoparticles and a fluid medium, wherein, when present, the solvent isremoved after combining the nanoparticles and the fluid medium to formthe nanocomposite fluid.

In another embodiment, a seal comprises an elastomer; and boron nitridenanoparticles disposed in the elastomer, wherein the seal is thermallyconductive and electrically insulating.

In an embodiment, a method for cutting a workpiece comprises disposingan electrode proximate to and spaced apart from the workpiece; disposingthe nanocomposite fluid of claim 1 between the electrode and theworkpiece; and passing an electric discharge through the nanocompositefluid to cut the downhole element.

In another embodiment, a process for cooling a downhole elementcomprises disposing a nanocomposite fluid downhole; and contacting thedownhole element with the nanocomposite fluid to cool the downholeelement.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawing, like elements are numberedalike:

The FIGURE shows a cross-section of a downhole, electric submersiblepump configured to use a nanocomposite fluid.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the FIGURE.

It has been found that a composition of electrically insulating andthermally conductive nanoparticles in a fluid medium provides thermalconduction and electrical resistance to the composition. Advantageously,the viscosity of the fluid and electrical characteristics can be tunedby varying the amount of the nanoparticles in the fluid medium. Suchfluids are useful as materials for thermal management and electricalinsulation. Additionally, compositions of the nanoparticles andelastomers can be combined to provide electrically insulating, thermallyconductive articles such as seals.

In an embodiment, a nanocomposite fluid includes a fluid medium and ananoparticle composition that includes nanoparticles that areelectrically insulating and thermally conductive. According to anembodiment, the nanoparticles are boron nitride.

Boron nitride is amorphous or crystalline, with at least three crystalforms (hexagonal, cubic, and wurtzite). Hexagonal boron nitride (h-BN)is structurally similar to graphite and also occurs in separated layersof covalently bound boron nitride. Cubic boron nitride (c-BN) is similarto the diamond allotrope of carbon and has a sphalerite structure.Wurtzite boron nitride (w-BN) has a structure similar to that of thelonsdaleite carbon polymorph, having tetrahedrally bonded boron andnitrogen atoms in a hexagonal covalent network. However, unlike the someof the corresponding carbon forms, boron nitride is electricallyinsulating with a high degree of thermal conductivity.

Nanoparticles are generally particles having an average particle size,in at least one dimension, of less than one micrometer (μm). As usedherein “average particle size” refers to the number average particlesize based on the largest linear dimension of the nanoparticle(sometimes referred to as “diameter”). Particle size, including average,maximum, and minimum particle sizes, can be determined by an appropriatemethod of sizing particles such as, for example, static or dynamic lightscattering (SLS or DLS) using a laser light source. Nanoparticlesinclude both particles having an average particle size of 250 nanometers(nm) or less, and particles having an average particle size of greaterthan 250 nm to less than 1 μm (sometimes referred in the art as“sub-micron sized” particles). In an embodiment, a nanoparticle has anaverage particle size of about 0.1 to about 500 nm, in anotherembodiment, 0.5 to 250 nm, in another embodiment, about 1 to about 150nm, and in another embodiment about 1 to about 75 nm. The nanoparticlesare monodisperse, where all particles are of the same size with littlevariation, or polydisperse, where the particles have a range of sizesand are averaged. Generally, polydisperse nanoparticles are used. Inanother embodiment, nanoparticles of different average particle sizesare used, and in this way, the particle size distribution of thenanoparticles is unimodal (exhibiting a single distribution), bimodalexhibiting two distributions, or multi-modal, exhibiting more than oneparticle size distribution.

The minimum particle size for the smallest 5% of the nanoparticles isless than 0.5 nm, in an embodiment less than or equal to 0.2 nm, and inanother embodiment less than or equal to 0.1 nm. Similarly, the maximumparticle size for 95% of the nanoparticles is greater than or equal to900 nm, in an embodiment greater than or equal to 750 nm, and in anotherembodiment greater than or equal to 500 nm.

The nanoparticles have a high surface area of greater than 180 m²/g, inan embodiment, 300 m²/g to 1800 m²/g, and in another embodiment 500 m²/gto 1500 m²/g.

Examples of the nanoparticle material include nanotubes, nanospheres,nanosheets, nanowires, nanorods, or a combination comprising at leastone of the foregoing.

Nanotubes (also referred to as boron nitride nanotubes (BNNT)) aretubular (fullerene-like) structures having open or closed ends and aremade entirely or partially of boron and nitrogen. In an embodiment,nanotubes include additional components such as chalcogens, nonmetals,or metalloids, which are incorporated into the structure of thenanotube, included as a dopant, form a surface coating, or a combinationcomprising at least one of the foregoing. However, no additionalcomponent is included that causes the nanoparticles to conductelectricity or to become thermally insulating. Nanotubes can be singlewalled nanotubes (SWNTs) or multi-walled nanotubes (MWNTs). BNNTs can beprepared in a similar manner as the corresponding carbon nanotubes. Theaspect ratio, i.e., the ratio of the length of the nanotube to itsdiameter, can be about 1 to about 700, specifically about 5 to about500, and more specifically about 10 to about 400.

Nanospheres (also referred to as boron nitride nanospheres (BNNS))include cage-like hollow allotropic forms of boron nitride possessing apolyhedral structure. Nanospheres include, for example, structureshaving about 20 to about 100 carbon atoms. For example, B₁₂N₁₂ is ananosphere having 24 total atoms and can include different polygons(e.g., squares and hexagons) in its structure. Other nanospherestructures may include polygons having an odd number of atoms. Withappropriate choice of starting materials, BN nanospheres can be preparedin a similar matter as the corresponding carbon fullerenes. For example,BN nanospheres can be made under CVD conditions starting from trimethoxyborane and ammonia. The diameter of the nanospheres can be from about 5nm to less than 1 μm, specifically about 5 nm to about 900 nm, and morespecifically about 5 nm to about 800 nm.

Nanosheet (also referred to a boron nitride nanosheet) is a cluster ofplate-like sheets of h-BN having a stacked structure of one or morelayers of h-BN (a plate-like two-dimensional structure of fusedhexagonal rings made of covalently bonded boron and nitrogen atoms)electrostatically bonded to one another. Nanosheet has both micro- andnano-scale dimensions, such as for example an average particle size of 1to 20 μm, in an embodiment 1 to 15 μm, and an average thickness(smallest) dimension in nano-scale dimensions, and an average thicknessof less than 1 μm, in an embodiment less than or equal to 700 nm, inanother embodiment less than or equal to 500 nm, in yet anotherembodiment less than or equal to 50 nm, in an embodiment less than orequal to 25 nm, and in a further embodiment less than or equal to 10 nm

In an embodiment, the nanoparticle is h-BN including nanosheet and h-BNfibers (i.e., h-BN particles having an average largest dimension ofgreater than 1 μm, a second dimension of less than 1 μm, and an aspectratio of greater than 10, where the h-BN particles form an inter-bondedchain). An exemplary nanosheet has an average particle size of 1 to 5μm, and in an embodiment 2 to 4 μm. In another embodiment, smallernanoparticles or sub-micron sized particles are combined withnanoparticles having an average particle size of greater than or equalto 1 μm. In a specific embodiment, the nanoparticle is a derivatizednanosheet. In another embodiment, the nanoparticle is a nanosheet havingtwo sheets of h-BN.

Nanosheet, can be prepared by, for example, exfoliation of a thickernanosheet (i.e., from a nanosheet having more layers of h-BN) or by asynthetic procedure by “unzipping” a BN nanotube to form a nanosheetribbon, which can be followed by derivatization of the nanosheet toprepare a nanosheet oxide. Exfoliation to form thinner nanosheet iscarried out by exfoliation of a nanosheet source such as nanosheet orintercalated nanosheet (where, e.g., an atom or compound is disposed inthe register of the nanosheet). Exemplary exfoliation methods include,but are not limited to, fluorination, acid intercalation, acidintercalation followed by high temperature treatment, and the like, or acombination comprising at least one of the foregoing. Alternatively,exfoliation can be accomplished by contacting a nanosheet with anadhesive tape and peeling the tape from the nanosheet to produce twothinner nanosheets. Exfoliation of the nanosheet provides a nanosheethaving fewer layers than non-exfoliated nanosheet. It will beappreciated that exfoliation of nanosheet may provide the nanosheet as asingle sheet only one molecule thick, or as a layered stack ofrelatively few sheets. In an embodiment, exfoliated nanosheet has fewerthan 50 single sheet layers, in an embodiment fewer than 20 single sheetlayers, in another embodiment fewer than 10 single sheet layers, and inanother embodiment fewer than 5 single sheet layers.

The BN nanoparticles can be derivatized to include a variety ofdifferent functional groups such as, for example, hydroxy, epoxy, ether,ketone, amine, alkoxy, alkyl, aryl, aralkyl, alkaryl, lactone,functionalized polymeric or oligomeric groups, and the like. In anembodiment, the nanoparticle is functionalized to include a hydrophilicfunctional group including hydroxy, carboxylic acid, amine, lactone,polyethylene glycol, a hydrophilic polymer, or a combination comprisingat least one of the foregoing. In another embodiment, nanoparticlesinclude a combination of derivatized nanoparticles and underivatizednanoparticles. According to an embodiment, the functional group is aalkyl group, hydroxyl group, or a combination comprising at least one ofthe foregoing. Such functional groups aid dispersion of the boronnitride nanoparticles in a variety of fluid media. In an embodiment, thefunctional group is the hydroxy group, which allows dispersal of theboron nitride nanoparticles in an aqueous fluid medium. In a furtherembodiment, the functional group is a C2-C100 alkyl group (branched orlinear, which can be substituted with a heteroatom) to disperse theboron nitride nanoparticles in an oil containing fluid medium.

In addition to the boron nitride nanoparticles, the nanocomposite fluidincludes a fluid medium. The nanocomposite fluid including the fluidmedium herein is useful as a fluid in, for example, an electricsubmersible pump (ESP), electric transformer, motor, electric dischargemachining, and like devices and environments where electricallyinsulating fluids and/or thermally conductive fluids are used. In anembodiment, the fluid medium is a hydrophilic fluid. Alternatively, thefluid medium is a hydrophobic fluid. In some embodiments, thenanocomposite fluid can be amphiphilic. Examples of the fluid mediuminclude water, oil, synthetic oil (e.g., fluorinated oils andsilicon-containing oils), distillate oil, or a combination comprising atleast one of the foregoing. The fluid medium is a dielectric; therefore,in the case of aqueous fluid media, for example water, de-ionized watercan be used. Further, electrolytic components (for example, watersoluble salts or ionic compounds) are not included in the fluid mediumor nanocomposite fluid. Alternatively, the nanocomposite fluid issubstantially free of electrolytic components.

Exemplary hydrophilic fluid media include but are not limited to water(which will be understood to be de-ionized water), C1-C10 alcohols(including polyhydric compounds), ammonia, ethers (e.g., dimethyl ether,diethyl ether), tetrahydrofuran, dioxane, esters (e.g., methyl acetate),ketones (e.g., acetone), aldehydes (e.g., acetaldehyde), or acombination comprising at least one of the foregoing.

Suitable hydrophobic fluid media are hydrocarbon-based and can be oils(also referred to as natural oils), distillate oils, or synthetic oils,or a combination thereof. As used herein, “natural oil” refers to anaturally occurring liquid or crude oil comprising a mixture ofhydrocarbons having various molecular weights, which may have beenrecovered from a subsurface rock formation, and which may have beensubjected to a refining process by distillation or otherwise. As usedherein, synthetic oil refers to a hydrocarbon liquid that compriseschemical compounds not originally present in a natural oil, but wereinstead synthesized from other compounds.

The fluid medium can be any natural oil, various petroleum distillates,or synthetic oil in any rheological form, including liquid oil, grease,gel, oil-soluble polymer composition, or the like, particularly themineral base stocks or synthetic base stocks used in the lubricationindustry, e.g., Group I (solvent refined mineral oils), Group II(hydrocracked mineral oils), Group III (severely hydrocracked oils,sometimes described as synthetic or semi-synthetic oils), Group IV(polyalphaolefins (PAOs)), and Group V (esters (e.g., polyols esters),naphthenes, polyalkylene glycols, silicone oil, fluorinated compounds(e.g., polyhexafluoropropylene oxide, perfluoropolyether (PFPE),perfluoroalkylether (PFAE), and perfluoropolyalkylether (PFPAE)), andthe like). Examples include polyalphaolefins, synthetic esters, andpolyalkylglycols.

Synthetic oils include hydrocarbon oils and halo-substituted hydrocarbonoils such as polymerized and interpolymerized olefins (e.g.,polybutylenes, polypropylenes, propylene-isobutylene copolymers,chlorinated polybutylenes, poly(1-octenes), poly(1-decenes), etc., andmixtures thereof); alkylbenzenes (e.g., dodecylbenzenes,tetradecylbenzenes, dinonylbenzenes, di-(2-ethylhexyl), benzenes, etc.);polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenyls, etc.);alkylated diphenyl ethers; alkylated diphenyl sulfides; derivatives,analogs and homologs thereof; and the like. Alkylene oxide polymers andinterpolymers and derivatives thereof where the terminal hydroxyl groupshave been modified by esterification, etherification, etc., constituteanother class of synthetic oils. Combinations of the synthetic oils canbe used together.

Another suitable class of synthetic oils includes the esters ofdicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinicacids, alkenyl succinic acids, maleic acid, azelaic acid, suberic acid,sebacic acid, fumaric acid, adipic acid, alkenyl malonic acids, etc.)with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecylalcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycolmonoalkylethers, propylene glycol, etc.). Specific examples of theseesters include dibutyl adipate, di(2-ethylhexyl)sebacate, di-hexylfumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azealate,dioctyl phthalate, didecyl phthalate, dicicosyl sebacate, the2-ethylhexyl diester of linoleic acid dimer, the complex ester formed byreacting one mole of sebacic acid with two moles of tetraethylene glycoland two moles of 2-ethylhexanoic acid, and the like.

Esters useful as synthetic oils also include those made from C5 to C12monocarboxylic acids and polyols and polyol ethers such as neopentylglycol, trimethylolpropane, pentaerythritol, dipentaerythritol,tripentaerythritol, etc. Other synthetic oils include liquid esters ofphosphorus-containing acids (e.g., tricresyl phosphate, trioctylphosphate, diethyl ester of decylphosphonic acid, etc.), polymerictetrahydrofurans and the like.

In a non-limiting embodiment, the nanocomposite fluid includes the fluidmedium and the nanoparticle composition. The nanoparticle composition(excluding functional groups) is present in an amount of about 0.001weight percent (wt %) to about 15 wt %, specifically about 0.01 wt % toabout 10 wt %, and more specifically about 0.01 wt % to about 5 wt %,based on the weight of the nanocomposite fluid. In an embodiment, thebalance of the nanocomposite fluid is the fluid medium. According toanother embodiment, the fluid medium is present in an amount of about 20wt % to about 99.999 wt %, specifically about 30 wt % to about 90 wt %,and more specifically about 40 wt % to about 85 wt %, based on theweight of the nanocomposite fluid.

The nanoparticle composition can include more than one type ofnanoparticle. According to an embodiment, the nanoparticle compositionincludes a first boron nitride nanoparticle and a second boron nitridenanoparticle. The first boron nitride nanoparticle can be present in anamount of about 0.001 wt % to about 15 wt %, specifically about 0.01 wt% to about 10 wt %, and more specifically about 0.01 wt % to about 5 wt%, based on the weight of the nanocomposite fluid. Likewise, the secondboron nitride nanoparticle can be present in an amount of about 0.001 wt% to about 15 wt %, specifically about 0.01 wt % to about 10 wt %, andmore specifically about 0.01 wt % to about 5 wt %, based on the weightof the nanocomposite fluid. In an embodiment, the first and secondnanoparticle can be any boron nitride nanoparticle herein. Particularly,the first nanoparticle is a boron nitride nanotube, and the secondnanoparticle is a boron nitride nanosphere. More particularly, the BNNTis present in amount of about 0.001 wt % to about 2 wt %, and the BNNSis present in an amount of about 0.001 wt % to about 5 wt %.

The nanocomposite fluid can have additives that tailor the fluidproperties for use in many different conditions such as aqueous orhydrocarbon environments, various temperature and/or pressure ranges,viscosity-dependent processes, and the like. Exemplary additives includebut are not limited to a microparticle, ceramic, surfactant, solvent,additive nanoparticle (which is different than the nanoparticlesdiscussed above, i.e., the boron nitride nanoparticles), or acombination comprising at least one of the foregoing. The nanocompositefluid can include additional chemical compounds, including but notlimited to, anti-oxidants, detergents, friction modifiers, viscositymodifiers, corrosion inhibiting additives, anti-wear additives,anti-foam agents, conditioners, and the like. Combinations of theadditives and chemical compounds can be used. The additives andadditional chemical compounds should not cause the nanocomposite fluidto substantially decrease its dielectric strength or thermalconductivity so as to electrically breakdown or become thermallyinsulating. It should be appreciated that, in some instances, anadditive may slightly increase the electrical conductivity or slightlydecrease the thermal conductivity of the nanocomposite fluid. As usedherein, “slightly” refers to a change in the electrical and thermalproperties by a relative difference of less than 20% of the originalvalue.

In an embodiment, the nanocomposite fluid can include microparticles. Asused herein, microparticles include particles having an average particlesize of greater than or equal to about 1 micrometer (μm), particularlyabout 1 μm to about 250 μm, more particularly about 1 μm to about 200μm, and even more particularly about 1 μm to about 150 μm.

Additive microparticles may be formed from any suitable additivematerial. In an exemplary embodiment, additive microparticles can beformed from the same material as the nanoparticles, i.e., the additivemicroparticles are boron nitride. In another exemplary embodiment,additive microparticles can be formed from a different material thanthat of the nanoparticles. In one exemplary embodiment, microparticlescomprise diamond microparticles.

Exemplary additive nanoparticles or microparticles can include, but arenot limited to a fullerene, graphene (including nanographene andnanographite platelets), graphite (including graphite fiber),nanodiamond, ceramic, carbon nanotubes, inorganic nanotubes, carbonnano-onions, nanowires, nanorods, polysilsesquioxanes, nanoclays, or acombination comprising at least one of the foregoing. In an embodiment,the additive nanoparticle is at least slightly suspended in thenanocomposite fluid. Exemplary shapes of the individual additivenanoparticles can include single or multi-walled nanotubes, spheres,balls, platelets, sheets, ribbons, and annular shapes. Dimensions of theadditive nanoparticles are similar to or the same as the boron nitridenanoparticles herein. For example, the additive nanoparticles can have aunimodal or multimodal size distribution.

Additive carbon nanoparticles may include various graphite, graphene,single-wall or multi-walled carbon nanotubes, fullerene, nanodiamond, ora combination thereof. Exemplary fullerenes include buckeyballs,buckeyball clusters, buckeypapers, single-wall carbon nanotubes ormulti-wall carbon nanotubes, or a combination thereof. Additiveinorganic nanoparticles may include, for example, various ceramicnanoparticles, including combinations thereof.

The additive nanoparticles or microparticles used herein can have anysuitable shape, including various spherical, tubular and plate-like orplanar shapes. These shapes may be symmetrical, irregular, or elongatedshapes. They may have a low aspect ratio (i.e., largest dimension tosmallest dimension) of less than 10 and approaching 1 in variousspherical particles. They also can have a two-dimensional aspect ratio(i.e., diameter to thickness for elongated additive nanoparticles suchas carbon nanotubes or diamondoids; or ratios of length to width, at anassumed thickness or surface area to cross-sectional area for plate-likeadditive nanoparticles such as, for example, nanographene or nanoclays)of greater than or equal to 10, specifically greater than or equal to100, more specifically greater than or equal to 200, and still morespecifically greater than or equal to 500. Similarly, thetwo-dimensional aspect ratio for such additive nanoparticles may be lessthan or equal to 10,000, specifically less than or equal to 5,000, andstill more specifically less than or equal to 1,000.

Fullerene additive nanoparticles, as disclosed herein, may include anyof the known cage-like hollow allotropic forms of carbon possessing apolyhedral structure. Fullerenes may include, for example, polyhedralbuckeyballs of about 20 to about 100 carbon atoms. For example, C₆₀ is afullerene having 60 carbon atoms and high symmetry (D_(5h)), and is arelatively common, commercially available fullerene. Exemplaryfullerenes include, for example, C₃₀, C₃₂, C₃₄, C₃₈, C₄₀, C₄₂, C₄₄, C₄₆,C₄₈, C₅₀, C₅₂, C₆₀, C₇₀, C₇₆, and the like. Fullerene nanoparticles mayalso include buckeyball clusters. A carbon nanotube is a carbon-based,tubular fullerene structure having open or closed ends and which may bemade entirely or partially of carbon, and may also include componentssuch as metals or metalloids. Additive nanotubes, including carbonnanotubes, may be single-wall nanotubes (SWNTs) or multi-wall nanotubes(MWNTs).

An additive graphite nanoparticle or microparticle includes a cluster ofplate-like or planar sheets of graphite, in which a stacked structure ofone or more layers of the graphite, which has a plate-like twodimensional structure of fused hexagonal rings with an extendeddelocalized π-electron system, layered and weakly bonded to one anotherthrough π-π stacking interaction. Additive graphene nanoparticles, maybe a single sheet or several sheets of graphene (e.g., nanographiteplatelets) having nano-scale dimensions, such as an average particlesize (average largest dimension) of less than e.g., 500 nanometers (nm),or in other embodiments may have an average largest dimension less thanabout 1000 nm. Additive nanographene may be prepared by exfoliation ofnanographite or by catalytic bond-breaking of a series of carbon-carbonbonds in a carbon nanotube to form a nanographene ribbon by an“unzipping” process, followed by derivatization of the nanographene toprepare, for example, an additive nanographene oxide.

Diamondoids can include carbon cage molecules such as those based onadamantane (C₁₀H₁₆), which is the smallest unit cage structure of thediamond crystal lattice, as well as variants of adamantane (e.g.,molecules in which other atoms (e.g., N, O, Si, or S) are substitutedfor carbon atoms in the molecule) and carbon cage polyadamantanemolecules including between 2 and about 20 adamantane cages per molecule(e.g., diamantane, triamantane, tetramantane, pentamantane, hexamantane,heptamantane, and the like).

Additive ceramic (microparticles and/or additive nanoparticles) is notparticularly limited and can be selected depending on the particularapplication of the nanocomposite fluid. Examples of the ceramic includean oxide-based ceramic, nitride-based ceramic, carbide-based ceramic,boride-based ceramic, silicide-based ceramic, or a combination thereof.In an embodiment, the oxide-based ceramic is silica (SiO₂) or titania(TiO₂). The oxide-based ceramic, nitride-based ceramic, carbide-basedceramic, boride-based ceramic, or silicide-based ceramic can contain anonmetal such as oxygen, nitrogen, boron, carbon, or silicon; a metalsuch as aluminum, lead, or bismuth; a transition metal such as niobium,tungsten, titanium, zirconium, hafnium, or yttrium; an alkali metal suchas lithium or potassium; an alkaline earth metal such as calcium,magnesium, or strontium; a rare earth such as lanthanum or cerium; and ahalogen such as fluorine or chlorine.

Polysilsesquioxanes, also referred to as polyorganosilsesquioxanes orpolyhedral oligomeric silsesquioxanes (POSS) derivatives arepolyorganosilicon oxide compounds of general formula RSiO_(1.5) (where Ris an organic group such as methyl) having defined closed or open cagestructures (closo or nido structures). Polysilsesquioxanes, includingPOSS structures, can be prepared by acid and/or base-catalyzedcondensation of functionalized silicon-containing monomers such astetraalkoxysilanes (including tetramethoxysilane and tetraethoxysilane)and alkyltrialkoxysilanes (such as methyltrimethoxysilane andmethyltriethoxysilane).

Nanoclays are hydrated or anhydrous silicate minerals with a layeredstructure and include, for example, alumino-silicate clays such askaolins including hallyosite, smectites including montmorillonite,illite, and the like. Exemplary nanoclays include those marketed underthe tradename CLOISITE® marketed by Southern Clay Additives, Inc.Nanoclays are exfoliated to separate individual sheets, or arenon-exfoliated, and further, are dehydrated or included as hydratedminerals. Other nano-sized mineral fillers of similar structure are alsoincluded such as, for example, talc, micas including muscovite,phlogopite, phengite, or the like.

The additive nanoparticles or microparticles can be functionalized toform a derivatized additive nanoparticle or derivatized microparticleusing either inorganic or organic materials. In an embodiment, theadditive nanoparticles or microparticles described herein can befunctionalized by being coated with a chemically bonded inorganicmaterial, including an inorganic material including a metal boride,carbide, nitride, carbonate, bicarbonate, or combinations thereof.According to another embodiment, the additive nanoparticles can befunctionalized to form a derivatized additive nanoparticle that includesan organic functional group such as carboxy, epoxy, ether, ketone,amine, hydroxy, alkoxy, alkyl, lactone, aryl functional group, apolymeric or oligomeric group thereof, or a combination comprising atleast one of the foregoing. In yet another embodiment, a variety offunctional groups can be appended to the additive nanoparticles ormicroparticles. Exemplary functional groups include, but are not limitedto, hydrocarbon and/or hydrocarbon derivatives. In certain embodiments,the functional group can be an alkyl, alkenyl, aromatic hydrocarbon, ormixtures or derivatives of these groups, or polymers of such. Exemplaryalkyl groups include those of about 1 to about 50 carbon atoms (straightchain or branched) or polymeric species containing about 10 to about20,000 carbon atoms. Optionally, the functional group can include aheteroatom, e.g., oxygen, sulfur, nitrogen, and the like. In certainembodiments, the functional group is hydrophobic.

In an exemplary embodiment, the derivatized additive nanoparticles arecharacterized by chemical bonding of the functionalizing material, suchas an organic group, to the additive nanoparticles (or microparticles),particularly to the surface of the additive nanoparticles. This is incontrast, for example, to adsorption of surfactants on the surface ofvarious additive nanoparticles or boron nitride nanoparticles used inthe nanocomposite fluid.

In an embodiment, the additive nanoparticles (or microparticles) includecarbon nanotubes, fullerenes, graphene including nanographene andgraphene fiber, nano graphite, nanodiamonds, polysilsesquioxanes,inorganic nanoparticles including silica nanoparticles, nanoclays, orcombinations comprising at least one of the foregoing.

The additive nanoparticles are chemically modified (e.g., by oxidationor derivatization) to have a resistivity effective to be non-conductiveso that the nanocomposite fluid maintains its electrical insulatingproperty and thermal conductivity. In an embodiment, the additivenanoparticle (e.g., additive carbon nanoparticle) is electricallyinsulating to maintain the nanocomposite fluid with a dielectricstrength greater than or equal to 80 kV/cm.

In certain embodiments, the additive nanoparticle or microparticle canbe present in an amount up to about 30% by volume, i.e., 30 volumepercent (vol %), based on the volume of the nanocomposite fluid.Alternatively, the additive nanoparticle can be present in an amount upto about 20 vol %, based on the volume of the nanocomposite fluid. Inother embodiments, the additive nanoparticle can be present in an amountup to about 10 vol %, based on the volume of the nanocomposite fluid. Incertain embodiments, the additive nanoparticle can be present in anamount of about 0.001 vol % to about 15 vol %, specifically about 0.001vol % to about 10 vol %, based on the volume of the nanocomposite fluid.Alternatively, the additive nanoparticle can be present in an amount ofabout 0.001 vol % to about 5 vol %, based on the volume of thenanocomposite fluid. In certain embodiments, the additive nanoparticlecan be present in an amount of about 0.1 ppm to about 5 vol %,alternatively about 0.1 ppm to about 10 vol %, or further alternativelyabout 0.1 ppm to about 15 vol %, based on the volume of thenanocomposite fluid. In certain embodiments, the additive nanoparticleis present in an amount of at least 0.1 ppm, alternatively at leastabout 1 ppm, further alternatively at least about 10 ppm, or at leastabout 100 ppm, based on the volume of the nanocomposite fluid.

In some embodiments, the nanocomposite fluid includes more than one typeof additive nanoparticle (or microparticle), wherein the total amount ofadditives can be up to about 30 vol %, specifically up to about 20 vol%, and more specifically up to about 10 vol %, based on the volume ofthe nanocomposite fluid. In other embodiments having more than one typeof additive nanoparticles, the total concentration of additives can beabout 0.001 vol % to about 15 vol %, based on the volume of thenanocomposite fluid.

Surfactants useful in the nanocomposite fluid include but are notlimited to nonionic surfactants. Exemplary nonionic surfactants includefatty alcohols (e.g., cetyl alcohol, stearyl alcohol, cetostearylalcohol, oleyl alcohol, and the like), polyoxyethylene glycol alkylethers (e.g., octaethylene glycol monododecyl ether, pentaethyleneglycol monododecyl ether, and the like), polyoxypropylene glycol alkylethers (e.g., butapropylene glycol monononyl ehther), glucoside alkylethers (e.g., decyl glucoside, lauryl glucoside, octyl glucoside),polyoxyethylene glycol octylphenol ethers (e.g., Triton X-100 (octylphenol ethoxylate)), polyoxyethylene glycol alkylphenol ethers (e.g.,nonoxynol-9), glycerol alkyl esters (e.g., glyceryl laurate),polyoxyethylene glycol sorbitan alkyl esters (e.g., polysorbates such assorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate,sorbitan tristearate, sorbitan monooleate, and the like), sorbitan alkylesters (e.g., polyoxyethylene sorbitan monolaurate, polyoxyethylenesorbitan monopalmitate, polyoxyethylene sorbitan monostearate,polyoxyethylene sorbitan monooleate, and the like), cocamideethanolamines (e.g., cocamide monoethanolamine, cocamide diethanolamine,and the like), amine oxides (e.g., dodecyldimethylamine oxide,tetradecyldimethylamine oxide, hexadecyl dimethylamine oxide,octadecylamine oxide, and the like), block copolymers of polyethyleneglycol and polypropylene glycol (e.g., poloxamers available under thetrade name Pluronics, available from BASF), and polyethoxylated amines(e.g., polyethoxylated tallow amine).

The amount of the surfactant within the nanocomposite fluid can be about0.05 wt % to about 50 wt %, specifically about 0.1 wt % to about 40 wt%, and more specifically about 1 wt % to about 25 wt %, based on theweight of the nanocomposite fluid.

According to an embodiment, the nanocomposite fluid includes a solvent.The solvent can be selected to be miscible with the fluid medium. In anembodiment, the solvent is an aprotic solvent. Examples of the aproticsolvent include tetrahydrofuran, dimethylformamide, ethyl acetate,acetone, acetonitrile, and the like. According to another embodiment,the solvent is a non-polar solvent or can be slightly polar. Examples ofthe non-polar solvent include hexane, pentane, diethyl ether, and thelike. The amount of the solvent within the nanocomposite fluid can beabout 0.05 wt % to about 50 wt %, specifically about 0.1 wt % to about40 wt %, and more specifically about 1 wt % to about 25 wt %, based onthe weight of the nanocomposite fluid.

In an embodiment, the nanocomposite fluid can be made by formingnanoparticles that are electrically insulating and thermally conductive,dispersing the boron nitride nanoparticles in a solvent, combining theboron nitride nanoparticles and a fluid medium, and removing the solventto form the nanocomposite fluid. According to an embodiment, thenanoparticles include boron nitride. Such nanoparticles are discussedabove.

The boron nitride nanoparticles can be produced by arc discharge,chemical vapor deposition, laser heating milled boron (at super-high orambient pressure), plasma-enhanced pulsed laser deposition, andhigh-temperature heating of h-BN powder. In an embodiment, boron is ballmilled to nano-sized particles that are mixed with a metal nitrate inethanol, and the composition is subsequently annealed under nitrogen toform boron nitride nanotubes. Here, the annealing conditions can controlthe size and structure of the boron nitride nanotubes. In anotherembodiment, boron nitride nanotubes can be produced from reacting boronpowder with magnesium oxide to produce B₂O₂, which is further reactedwith ammonia to produce the BNNTs. Alternatively, boron nitridenanospheres can be made in a chemical vapor deposition reactioninvolving B(OCH₃)₃ and ammonia at, for example, 900° C., followed byhigh-temperature annealing. According to yet another embodiment, boronnitride nanosheets (e.g., h-BN sheets) can be made by exfoliating h-BNfrom thicker sheets with adhesive tape (or a chemical exfoliant).

The boron nitride nanoparticles are dispersed in a solvent, which is thesame or different than the solvent that is optionally present in thefinished nanocomposite fluid. The solvent has a low boiling point, forexample, less than 120° C., more particularly less than 100° C. Thesolvent can be, for example, acetone, dichloromethane, tetrahydrofuran,ethyl acetate, acetonitrile, methanol, ethanol, propanol, water, or acombination comprising at least one of the foregoing.

The boron nitride nanoparticles and solvent are then combined with thefluid medium. This composition is held at about room temperature (e.g.,about 10° C. to about 35° C.) and under vacuum (e.g., less than 760 torr(101325 pascals) such as about 30 millitorr (4 pascal)) for less than anhour (e.g., about 15 minutes). The solvent is removed during this time.Reactions between the solvent and the fluid medium are avoided byadjusting the temperature and the time that the solvent is present inthe composition. After the solvent is removed, the nanocomposite fluidis ready for further use. According to another embodiment, thenanoparticles are suspended in a non-ionic surfactant and then combinedwith the fluid medium to form the nanocomposite fluid. In yet anotherembodiment, the nanoparticles are suspended in a solvent and asurfactant. For some embodiments that include suspending thenanoparticles in the solvent, the solvent is removed after combiningwith the fluid medium as previously discussed. At this time, additivescan be added to the nanocomposite fluid. Alternatively, the additivescan be added prior to combining the boron nitride nanoparticles with thesolvent and/or the fluid medium. As a further alternative, thecomposition can be at a temperature from about 0° C. to about 100° C.,specifically about 5° C. to about 80° C., and more specifically about10° C. to about 50° C. under vacuum as the solvent is removed.

To suspend the boron nitride nanoparticles in the fluid medium, thenanoparticles can be derivatized with a functional group. In anembodiment, the functional group is hydroxy so that the nanoparticlesare suspended in an aqueous fluid medium (e.g., deionized water). Inanother embodiment, the functional group is an aliphatic group (forexample, a C1-C20 alkyl group) to disperse the nanoparticles in an oilcontaining fluid medium.

The nanoparticles are electrically insulating and thermally conductive.Additionally, the nanocomposite fluid is also electrically insulatingand thermally conductive due to the nanoparticles. To maintain theseproperties (electrically insulating and thermally conducting), the fluidmedia and/or additives (or other components) in the nanocomposite fluidare substantially electrically insulating and/or thermally conductive.For example, although carbon nanoparticles can be electricallyconductive, the carbon nanoparticles, when used as an additivenanoparticle, are modified (e.g., oxidized) to be electricallyinsulating. In this way, the thermal conductivity of the nanocompositefluid is about 0.1 Watts per meter per Kelvin (W/m K) to about 1.2 W/mK, specifically about 0.15 W/m K to about 1.1 W/m K, and morespecifically about 0.2 W/m K to about 1 W/m K. In some embodiments, thenanoparticles (e.g., boron nitride nanoparticles such as BNNTs or BNNSs)have a thermal conductivity of about 100 W/m K to about 9500 W/m K,specifically about 125 W/m K to about 8500 W/m K, and more specificallyabout 150 W/m K to about 8000 W/m K.

Such nanocomposite fluids beneficially provide a high dielectricstrength of greater than 6 megavolts per meter (MV/m), specificallygreater than 12 MV/m, more specifically greater than 65 MV/m, and evenmore specifically greater than 90 MV/m. In an embodiment, the dielectricstrength is about 6 MV/m to about 90 MV/m.

The nanocomposite fluids have a viscosity of about 0.5 centipoise (cps)to about 6 cps, specifically about 1 cps to about 6 cps, and morespecifically about 1 cps to about 5 cps.

Even though the fluid medium may be thermally conductive and/orelectrically insulating, the nanoparticles in the nanocomposite fluidenhance these properties by further increasing the thermal conductionand electrical insulation of the nanocomposite fluid. Moreover, acombination of various types of nanoparticles (e.g., BNNTs, BNNS, and/orboron nitride nanosheets) can be disposed in the nanocomposite fluid invarious compositional amounts to tune the fluid properties. Suchproperties include thermal, electrical, flow, and tribologicalproperties

Thus, in an embodiment, nanoparticles are dispersed in a fluid medium inan amount effective to result in an enhancement of a property such asincreased lubricity, increased thermal conductivity, increased heattransfer capacity, increased electrical insulation, increased control ofviscosity, or a combination comprising at least one of the foregoing. Assuch, the nanocomposite fluid, including the nanoparticles, can becharacterized as a thermal conductivity enhancer, electrical insulationenhancer, viscosity controller, or lubricity enhancer. In certainembodiments, thermal conductivity of the nanocomposite fluid is greaterthan the thermal conductivity of the base materials (nanoparticles andfluid medium) from which it is manufactured. Without wishing to be boundby any specific theory, this increased thermal conductivity may be dueto a combination of a high lattice conductivity of BN nanoparticles, anincreased surface-to-volume ratio of the nanoparticles as well asnanoconvection caused by Brownian motion of the nanoparticles. Heattransfer is directly proportional to the thermal conductivity. Ingeneral, an increase in thermal conductivity results in an increase inthe heat transfer through the matrix. When added to a matrix material,such as, the fluid medium (e.g., an oil), the nanoparticle's thermalproperties enhance the thermal conductivity of the matrix material.Dramatic increases in thermal conductivity occur when the nanoparticlesherein are added to water (de-ionized water) or other electricallynon-conductive solutions. Similarly, other physical properties, such asfor example, the viscosity of the fluid medium, can be changed byaddition of the nanoparticles. Although, boron nitride nanotubes canincrease the viscosity of the fluid medium, boron nitride nanospherescan also be added (while maintaining or decreasing the amount of theboron nitride nanotubes) to maintain the thermal conductivity ofnanocomposite fluid but decreasing the viscosity of the nanocompositefluid. In certain embodiments, to achieve a proper balance of desiredproperties of the nanocomposite fluid, a combination of differentamounts of nanoparticles, can be added to the fluid medium. In certainembodiments, the method can include adding additives in a concentrationof up to about 30 vol %, specifically up to about 20 vol %, and morespecifically up to about 10 vol %, based on the volume of thenanocomposite fluid.

Due to the thermal conductivity and electrical insulating properties ofthe nanocomposite fluids, they are useful as, for example, heatmanagement (e.g., as a coolant) and/or electrical insulation inenvironments such as high voltage or temperature-producing environmentsor equipment. Such environments include downhole environments havingdownhole articles such as a transformer, motor, pump, resistive heater,induction heater, drill bit, sensor, current source, or a combinationcomprising at least one of the foregoing.

In a non-limiting embodiment, a process for cooling a downhole elementincludes disposing the nanocomposite fluid downhole and contacting thedownhole element with the nanocomposite fluid to cool the downholeelement. The process can further include circulating the nanocompositefluid downhole and contacting the nanocomposite fluid with a heatexchanger to decrease the temperature of the nanocomposite fluid. Theheat exchanger can be located either at the surface or within aborehole.

According to an embodiment, a nanocomposite fluid described herein isused in a downhole electrical submersible pumping system (ESP) that isdisposed in a borehole, wherein the borehole may intersect asubterranean formation. As shown in the FIGURE, the ESP includes at alower end a motor 10, a seal (not shown), and a pump (not shown) on anupper end. The motor 10 and pump are separated by the seal. The motor 10includes a rotor 20 (or a plurality of rotors 20) and bearings 30mounted on a motor shaft 40 that is coupled to and drives the pump. Themotor shaft 40 is coupled to the pump via a seal section, and the motorshaft 40 is coupled to a shaft in the seal section, which in turn iscoupled to a shaft in the pump. The rotor 20 can be a hollow cylindermade of a stack of laminations, a copper bar and end rings, which issupported at each end by the bearings 30. The motor 10 is filled withnanocomposite fluid 50 having a composition as described herein andincludes a running clearance 60 located between the internal diameter ofthe stator 70 and outside diameter of the rotors 20 wherein thenanocomposite fluid 50 provides thermal conduction, electricalinsulation, and lubrication for items such as the bearings 30 in orderto carry away (dissipate) heat generated by friction from the rotor 20and windage losses while being an electrical insulator between thestator 70 and the rotor 20. The nanocomposite fluid 50 within therunning clearance 60 can be circulated within the motor 10 through ahole 80 in the shaft 40. The nanocomposite fluid 50 in the motor canalso be used in the seal and communicates and circulates between theseal and motor 10. The nanocomposite fluid 50 used in the seal assistswith the cooling of a bearing (e.g., a thrust bearing) in the seal. Thenanocomposite fluid 50 within the motor 10 and seal can include up toabout 30 vol % of nanoparticles, specifically up to about 20 vol % ofnanoparticles, and more specifically up to about 10 vol % ofnanoparticles, based on the volume of the nanocomposite fluid. Thenanoparticles are boron nitride nanoparticles and can be derivatizedwith functional groups. Further, the nanocomposite fluid can includeadditives such as, but not limited to, carbon nanotubes, carbonnano-onions, graphite nanoparticles, carbon nanotubes, nanodiamonds ortheir derivatives, ceramic nanop articles, or a combination comprisingat least one of the foregoing.

In another embodiment, the nanocomposite fluid is disposed in anelectrical transformer. Such transformers can be used to convert aninput voltage to an output voltage by stepping up or stepping down theinput voltage via inductive coupling. The input voltage may be generatedby an external power supply or by a downhole alternator using amultistage turbine or a mud motor driven by mud flow and connected to amagnetic shaft, which rotates within a windings package. During rotationof the magnetic shaft, a changing magnetic flux induces an electriccurrent in the windings of the windings package. The nanocomposite fluidprovides an additional electrical insulation to the windings and powerleads in the transformer, preventing electrical breakdown within thetransformer. Additionally, the nanocomposite fluid contacts the windingsand its core to, for example, absorb heat from them and can subsequentlyrelease the heat into a heat sink to cool the transformer bytransferring heat away from the windings and other elements that mayheat up within the transformer during operation. In some embodiments,the heat sink is the nanocomposite fluid. The nanocomposite fluid can becirculated and contact a heat exchanger or can continue to absorb heatfrom the transformer's components due to the heat capacity of thenanocomposite fluid.

In a non-limiting embodiment, a non-contact heater such as an inductionheater can be cooled or the components thereof electrically insulated bythe nanocomposite fluid. The induction heater can include a work coil(also referred to as an inductor), work head (containing, e.g., atransformer), and power unit. In an exemplary embodiment, powertransfers from the power unit to a workpiece via the work coil. The workcoil can be interposed between two dielectric members (e.g., ceramictubes such as concentric ceramic tubes), and the workpiece can bedisposed inside the inner ceramic tube or external to the outer ceramictube to be inductively heated by the work coil. The nanocomposite fluidcan contact the work coil between the dielectric members to transferheat from the work coil. In certain embodiments, the work coil caninclude an internal fluid channel through which the nanocomposite fluidcan flow in order to disperse heat from the work coil. Additionally, thenanocomposite fluid can be used to cool the power unit and work head.

According to another embodiment, the nanocomposite fluid is used as adielectric material in electric discharge machining (EDM). In EDM, apulsed electrical discharge forms an arc that passes between anelectrode (also referred to as tool electrode) and a workpiece (alsoreferred to as a workpiece electrode) through the dielectric material.As a result of the electrical discharges, matter is removed from theworkpiece. The nanocomposite fluid (e.g., a flow of nanocomposite fluid)insulates the electrode from the workpiece and can also remove debris(e.g., metal, including molten metal) from the work zone between theelectrode and the workpiece. Further, the nanocomposite fluid also caneffectively cool the workpiece near the discharge location, which mayprovide high machining tolerance. By performing EDM, for example, on adownhole element, the downhole element may be shaped or a portion (or,alternatively the entire element) completely disintegrated or cut awayfor removal from the downhole environment.

Thus, in an embodiment, a method for cutting a workpiece includesdisposing an electrode proximate to and spaced apart from the workpiece,disposing the nanocomposite between the electrode and the workpiece, andpassing an electric discharge through the nanocomposite fluid to cut (ormachine) the downhole element. The method further includes moving theelectrode to a new position of the workpiece. Further, the distancebetween the electrode and workpiece can be adjusted. Additionally, thenanocomposite fluid can flow between the electrode and the workpiece forremoving debris (including molten metal) therebetween. The debris caninclude material that has been removed from the workpiece or electrodeor material that is extraneous to the cutting process. According to anembodiment, the workpiece is a downhole element such as a valve,tubular, wire, cable, pin, bolt, anchor, clamp, and the like.

In an embodiment, the fluid medium of the nanocomposite fluid is anaqueous medium, particularly de-ionized water. Alternatively oradditionally, the fluid medium can include a high resistivity fluid thatis electrically insulating, which can have an electrical resistivity ofat least 10 megaohms centimeter (MQ cm), specifically at least 15 MΩ cm,and more specifically at least 20 MΩ cm, based on its resistivity at 25°C. An enclosing member may surround the electrode and workpiece toisolate these items from the downhole environment as the nanocompositefluid is introduced. Such an enclosure will preserve the nanocompositefluid from contaminants that would cause the nanocomposite fluid to havea decrease in its electrical insulating properties or becomeelectrically conductive. The nanocomposite fluid can be circulatedthrough the enclosing member to refresh the nanocomposite fluid betweenthe electrode and workpiece.

In an additional embodiment, the nanoparticles herein (e.g., BNNTs,BNNSs, BN nanosheets, and the like) can be used without the fluidmedium. According to an embodiment, a seal can include thenanoparticles. In an exemplary embodiment, a seal includes an elastomer;and boron nitride nanoparticles disposed in the elastomer, wherein theseal is thermally conductive and electrically insulating. The thermalconduction and electrical insulation properties of the seal derives atleast in part from the boron nitride nanoparticles. Due to addition ofthe nanoparticles, the electrical resistivity of the seal is greaterthan 1×10¹² ohm-cm, specifically greater than 1×10¹⁵ ohm-cm, and morespecifically greater than 1×10¹⁸ ohm-cm. In some embodiments, theelectrical resistivity can be about 1×10¹⁵ ohm-cm to about 1×10¹⁹ohm-cm. Additionally, the dielectric strength of the seal is equal to orgreater than 150 kV/mm, specifically equal to or greater than 200 kV/mm,and more specifically equal to or greater than 250 kV/mm. In certainembodiments, the dielectric strength is about 150 kV/mm to about 325kV/mm. The thermal conductivity of the seal can be about 0.5 W/m K toabout 5 W/m K, specifically about 1 W/m K to about 4 W/m K, and morespecifically about 1 W/m K to about 3 W/m K.

According to a non-limiting embodiment, the elastomer includespolytetrafluoroethylene (PTFE), nitrile-butyl rubber (NBR), hydrogenatednitrile-butyl rubber (HNBR), high fluorine content fluoroelastomerrubbers such as those in the FKM family and marketed under the tradenameVITON® fluoroelastomers (available from FKM-Industries) andperfluoroelastomers such as FFKM (also available from FKM-Industries)and marketed under the tradename KALREZ® perfluoroelastomers (availablefrom DuPont), and VECTOR® adhesives (available from Dexco LP),organopolysiloxanes such as functionalized or unfunctionalizedpolydimethylsiloxanes (PDMS), tetrafluoroethylene-propylene elastomericcopolymers such as those marketed under the tradename AFLAS® andmarketed by Asahi Glass Co., ethylene-propylene-diene monomer (EPDM)rubbers, polyvinylalcohol (PVA), and the like, and combinationscomprising at least one of the foregoing polymers.

The amount of the nanoparticles can be about 0.05 wt % to about 20 wt %,specifically about 0.5 wt % to about 15 wt %, and more specificallyabout 1 wt % to about 10 wt %, based on the weight of the seal. Acombination of boron nitride nanoparticles can be used in the seal, forexample, BNNTs and BNNSs can be disposed among the elastomer.

In a further embodiment, the seal can include the fluid medium hereinamong the chains of the elastomer. The seal can be impregnated with thefluid medium during making the seal or after. The fluid medium can beuniformly or non-uniformly disposed in the seal. In an embodiment, thefluid medium can penetrate from the surface of the seal to some depth ofthe seal in, for example, a concentration gradient. Such seals can beused in submersible pumps, valves, and the like. The seals can be anyshape including O-rings, T-rings, gaskets, and the like.

The seal can be made by compounding pellets of the elastomer with thenanoparticles, optionally adding the fluid medium to the composition,and then molding the composition into a shape. The elastomer can becured via application of heat or radiation, e.g., ultraviolet light, asa result of the presence of crosslinkable moieties of the elastomer oraddition of a crosslinking agent.

While one or more embodiments have been shown and described,modifications and substitutions may be made thereto without departingfrom the spirit and scope of the invention. Accordingly, it is to beunderstood that the present invention has been described by way ofillustrations and not limitation.

All ranges disclosed herein are inclusive of the endpoints, and theendpoints are independently combinable with each other. The suffix “(s)”as used herein is intended to include both the singular and the pluralof the term that it modifies, thereby including at least one of thatterm (e.g., the colorant(s) includes at least one colorants). “Optional”or “optionally” means that the subsequently described event orcircumstance can or cannot occur, and that the description includesinstances where the event occurs and instances where it does not. Asused herein, “combination” is inclusive of blends, mixtures, alloys,reaction products, and the like. All references are incorporated hereinby reference.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Further, it should further be noted that the terms “first,”“second,” and the like herein do not denote any order, quantity, orimportance, but rather are used to distinguish one element from another.The modifier “about” used in connection with a quantity is inclusive ofthe stated value and has the meaning dictated by the context (e.g., itincludes the degree of error associated with measurement of theparticular quantity).

What is claimed is:
 1. A nanocomposite fluid comprising: a fluid medium;and a nanoparticle composition comprising nanoparticles which areelectrically insulating and thermally conductive.
 2. The nanocompositefluid of claim 1, wherein the nanoparticles comprise boron nitride. 3.The nanocomposite fluid of claim 2, wherein the boron nitride isderivatized with a functional group.
 4. The nanocomposite fluid of claim3, wherein the functional group is a alkyl group, hydroxyl group, or acombination comprising at least one of the foregoing.
 5. Thenanocomposite fluid of claim 2, wherein the nanoparticle is a nanotube,nanosphere, nanosheet, nanowire, nanorod, or a combination comprising atleast one of the foregoing.
 6. The nanocomposite fluid of claim 5,wherein the nanoparticle is the nanotube which has an aspect ratio ofabout 10 to about
 400. 7. The nanocomposite fluid of claim 5, whereinthe nanoparticle is the nanosphere which has a diameter of about 5 nm toabout 800 nm.
 8. The nanocomposite fluid of claim 1, wherein the fluidmedium comprises de-ionized water, oil, synthetic oil, distillate oil,or a combination comprising at least one of the foregoing.
 9. Thenanocomposite fluid of claim 1, wherein the nanoparticle compositionincludes boron nitride nanotubes and boron nitride nanospheres.
 10. Thenanocomposite of claim 9, wherein the boron nitride nanotubes arepresent in an amount of about 0.001 wt % to about 10 wt %, the boronnitride nanospheres are present in an amount of about 0.001 wt % toabout 10 w %, based on the weight of the nanocomposite fluid.
 11. Thenanocomposite fluid of claim 1, further comprising boron nitridemicroparticles.
 12. The nanocomposite fluid of claim 1, furthercomprising a surfactant.
 13. The nanocomposite fluid of claim 12,wherein the surfactant is a fatty alcohol, polyoxyethylene glycol alkylether, polyoxypropylene glycol alkyl ether, glucoside alkyl ether,polyoxyethylene glycol octylphenol ether, polyoxyethylene glycolalkylphenol ether, glycerol alkyl ester, polyoxyethylene glycol sorbitanalkyl ester, sorbitan alkyl ester, cocamide ethanolamine, amine oxide,block copolymer comprising polyethylene glycol and polypropylene glycol,polyethoxylated amine, or a combination comprising at least one of theforegoing.
 14. The nanocomposite fluid of claim 1, further comprising asolvent.
 15. The nanocomposite fluid of claim 1, further comprising anadditive nanoparticle including carbon nanotubes, fullerenes,nanodiamonds, graphene, polysilsesquioxanes, inorganic nanoparticles,nanoclays, or a combination comprising at least one of the foregoing,wherein the nanocomposite fluid has a dielectric strength greater thanor equal to 80 kV/cm.
 16. The nanocomposite fluid of claim 1, whereinthe nanoparticle is present in an amount of about 0.01 wt % to about 10wt %, based on the weight of the nanocomposite fluid.
 17. Thenanocomposite fluid of claim 1, wherein the fluid medium is present inan amount of about 20 wt % to about 99.99 wt %, based on the weight ofthe nanocomposite fluid.
 18. The nanocomposite fluid of claim 1, whereinthe thermal conductivity of the nanocomposite fluid is about 0.2 W/m Kto about 1 W/m K.
 19. The nanocomposite fluid of claim 1, wherein thenanoparticles have a thermal conductivity of about 150 W/m K to about8000 W/m K.
 20. The nanocomposite fluid of claim 1, wherein thenanocomposite fluid has a dielectric strength at least about 80 kV/cm.21. The nanocomposite fluid of claim 1, wherein the viscosity of thefluid is about 1 cps to about 5 cps.
 22. A method of making ananocomposite fluid, comprising: forming nanoparticles which areelectrically insulating and thermally conductive, the nanoparticlesbeing comprised of boron nitride; suspending the nanoparticles in asolvent, surfactant, or a combination comprising at least one of theforegoing; and combining the nanoparticles and a fluid medium, wherein,when present, the solvent is removed after combining the nanoparticlesand the fluid medium to form the nanocomposite fluid.
 23. The method ofclaim 22, wherein the solvent has a boiling point which is less than100° C.
 24. The method of claim 23, wherein the solvent includesacetone, dichloromethane, tetrahydrofuran, ethyl acetate, acetonitrile,methanol, ethanol, propanol, water, or a combination comprising at leastone of the foregoing.
 25. The method of claim 22, wherein the method isperformed at a temperature which is less than about 30° C.
 26. Themethod of claim 22, wherein the method is performed at a pressure whichis less than 1 atmosphere (101,325 pascals).
 27. The method of claim 22,wherein the fluid medium is an oil or de-ionized water.
 28. The methodof claim 22, wherein the nanoparticles comprises a coating disposed onthe nanoparticle.
 29. A seal comprising: an elastomer; and boron nitridenanoparticles disposed in the elastomer, wherein the seal is thermallyconductive and electrically insulating.
 30. The seal of claim 29,wherein the electrical resistivity of the seal is greater than 1×10¹⁵ohm-cm.
 31. The seal of claim 29, wherein the dielectric strength of theseal is equal to or greater than 15 kV/cm.
 32. The seal of claim 29,wherein the thermal conductivity of the seal is about 1 W/m K to about 3W/m K.
 33. The seal of claim 29, wherein the elastomer includespolytetrafluoroethylene, nitrile-butyl rubber, hydrogenatednitrile-butyl rubber, fluoroelastomer rubber, or a combinationcomprising at least one of the foregoing.
 34. A method for cutting aworkpiece, comprising: disposing an electrode proximate to and spacedapart from the workpiece; disposing the nanocomposite fluid of claim 1between the electrode and the workpiece; and passing an electricdischarge through the nanocomposite fluid to cut the downhole element.35. The method of claim 34, further comprising moving the electrode to anew position of the workpiece.
 36. A process for cooling a downholeelement, comprising: disposing the nanocomposite fluid of claim 1downhole; and contacting the downhole element with the nanocompositefluid to cool the downhole element.
 37. The process of claim 36, furthercomprising: circulating the nanocomposite fluid downhole; and contactingthe nanocomposite fluid with a heat exchanger to decrease thetemperature of the nanocomposite fluid.
 38. The process of claim 36,wherein the downhole element is a transformer, motor, pump, resistiveheater, induction heater, drill bit, sensor, current source, or acombination comprising at least one of the foregoing.